. You buy hats for $5 and sell them for $20 each. There are no other expenses. What
does the graph of profits as a function of
the number of hats sold look like?

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.